The first bullseye The Dark Tower movie hit was casting its lead: Idris Elba as Roland Deschain, the last of the knights known as gunslingers, a lost man wandering an apocalyptic wasteland in search of the Man in Black, whose next stop on his march of destruction is our world.

The casting choice by director Nikolaj Arcel was a change from the novels. Stephen King had envisioned a Clint Eastwood-style, blue-eyed, white man as his six-shooting knight, but the author has applauded the choice of Elba for the lead character in his epic saga. Tough is tough; it doesn’t have a color.

Sunday during the BET Awards, Sony Pictures aired a new teaser for the Aug. 4 fantasy adventure that focused on the Mandela and Beasts of No Nation actor — and the royal legacy of his hero in The Dark Tower, a man seeking justice… although revenge will do, if that’s all that’s available.

In the story, the tower is a mythic structure at the nexus of all space and time. Its levels constitute different worlds and realities, and our world is stacked among them — a critical building block, actually. Matthew McConaughey’s magic-wielding Man in Black wants to bring it down, collapsing the worlds on each other and allowing his trapped master, the Crimson King, to be freed to rule them.

He needs others with power — like Jake Chambers (Tom Taylor), a boy from present-day New York who possesses a psychic ability known as a “shine” (an obvious homage to another classic King novel). By harnessing people with this strength, the Man in Black can use them to break through the dimensions and attack the tower.

So, by protecting the boy, Roland the Gunslinger is protecting these worlds. He does not hesitate to draw his irons to save Jake. He does wonder if we have guns and ammunition here — though he’s certain such weaponry is difficult to acquire and only available to the highly trained.